The present disclosure generally relates to the field of steam generator, and, more particularly, to an advanced molten salt once-through steam generator for solar thermal power plants.
Solar thermal power plants with molten salt have been introduced to the market focusing on base load operations. Such power plants are equipped with standard drum-type steam generator.
For example, in a conventional arrangement as depicted in FIG. 1, a steam generator 10 includes a superheater 11, an evaporator 12, an economizer 13, a reheater 14, and a steam drum 16, which are fluidically connected to receive feedwater from a feedwater source 18, which may be heated via a high presser heater 15, flowing from the economizer 13 to the superheater 11 to produce steam by using the heat of molten salt ‘MS’ flowing from the superheater 11 to the economizer 13. Further, in such conventional arrangement of the steam generator 10 with the steam drum 16, a recirculation line 19 of the feedwater from the economizer 13 outlet to the economizer 13 inlet, and, an economizer bypass 20, are included to work at high pressure, nearly 170 bar, in nominal load, and to maintain the feedwater inlet temperature to at least 245° C. at the same time and in full load and part load operation conditions to obtain efficient thermodynamics cycle and avoiding Molten Salt freezing at the economizer 13 inlet.
However, in upcoming years, more flexible power plants will be required, which may have to be suitable for fast load changes. In such a scenario, the conventional steam generator 10 with steam drum 16 may not be suitable to effectively accommodate with the power plant needs. This is due to presence of steam drum 16 in the steam generator 10 that reduces the flexibility the steam production depending upon the quick changes as per the load of the power plant. In addition to this, the recirculation line 19 and the economizer bypass 20 which are required to operate the steam generator 10 with steam drum 16 also increases the complexity.
Further, there are available other types of steam generators that do not include steam drum, such as, once-through steam generator (OTSG). The absence of steam drum may be suitable for quick changes in steam production and fewer variables to control. However, such OTSG are only ideal for cycling and base load operation and may not be equally suitable to be used with molten salt solar power plants due to temperature and pressure requirements of the feedwater, i.e. 170 bars and 245° C. Furthermore, use of the recirculation line and the economizer bypass as it is in the conventional steam drum 10, to maintain the parameter of the feedwater, in OTSG may be not suitable with molten salt due to removal of steam drum.
Accordingly, there exist a need to overcome the existing problem in the OTSG to make it suitable to be incorporated in a solar thermal power plant to enable thereto to fast load changes, suitability to frequent start-up and shut-down, suitability for producing steam at high temperature and pressure, and decrease water consumption along with weight reduction and compact integration.